Ayatollah Ali Khamenei, Iran's supreme leader ordered Monday a probe into claims of election fraud, one day after he stated the re-election of President Mahmoud Ahmadinejad was following a "fair" process. State television quoted Ayatollah Ali Khamenei directing the Guardian Council to look into charges by reformist candidate Mir Hossein Mousavi.

"Issues must be pursued through a legal channel," state TV quoted the Iranian leader as saying. Ayatollah Ali Khamenei said he has "insisted that the Guardian Council carefully probe this letter." State TV quoted Ayatollah Ali Khamenei urging Mousavi to try to keep the violence from escalating and saying "it is necessary that activities are done with dignity."

Meanwhile, thousands of people have staged a rally in central Tehran to show support for defeated reformist presidential candidate Mir-Hossein Moussavi despite a ban declared earlier in the day by Interior Ministry. According to Moussavi aides, there was not enough time to inform the supporters of the cancellation of the rally.

Press TV reported that Moussavi and another defeated presidential candidate Mehdi Karroubi were attending the rally to alleviate any possible conflict between pro-Moussavi supporters and anti-riot police forces.